Martin O. Onani

Indium phosphide-based semiconductor nanocrystals and their applications

Semiconductor nanocrystals or quantum dots (QDs) are nanometer-sized fluorescent materials with optical properties that can be fine-tuned by varying the core size or growing a shell around the core. They have recently found wide use in the biological field which has further enhanced their importance. This review focuses on the synthesis of indium phosphide (InP) colloidal semiconductor nanocrystals. The two synthetic techniques, namely, the hot-injection and heating-up methods are discussed. Different types of the InP-based QDs involving their use as core, core/shell, alloyed, and doped systems are reviewed. The use of inorganic shells for surface passivation is also highlighted. The paper is concluded by some highlights of the applications of these systems in biological studies.

Preparation and properties of the halogenoalkyl compounds [(η5-C5H5)(CO)2(PPhiMe3−i)Mo{(CH2)nX}] (n=3, 4; i=0–3; X=Br, I) and [{η5-C5(CH3)5}(CO)3Mo{(CH2)nX}] (n=3, 4; X=Br, I) and the crystal structures of [(η5-C5H5)(CO)3W{(CH2)5I}], [(η5-C5H5)(CO)3W{(CH2)3Br}] and [(η5-C5H5)(CO)2(PPh3)Mo{(CH2)3I}]

Abstract The compounds [Cp(CO)2(PPhiMe3−i)Mo{(CH2)nBr}] (Cp=η5-C5H5, n=3, 4; i=0–3) and [Cp*(CO)3Mo{(CH2)nBr}] (Cp*=η5-C5(CH3)5, n=3, 4) were prepared in medium to high yield by the reaction of the corresponding anion ([Cp(CO)2(PPhiMe3−i)Mo]− or [Cp*(CO)3Mo]−) with Br(CH2)nBr. The bromoalkyl compounds were subsequently reacted with NaI to give the corresponding iodoalkyl compounds [Cp(CO)2(PPhiMe3−i)Mo{(CH2)nI}] (n=3, 4; i=0–3) and [Cp*(CO)3Mo{(CH2)nI}] (n=3, 4). The iodoalkyl compounds can also be prepared by the reaction of the corresponding anion and α,ω-diiodoalkane in much lower yields. These compounds have been fully characterised and their properties are discussed. The crystal and molecular structure of [Cp(CO)2(PPh3)Mo{(CH2)3I}] is reported. The compound forms crystals in the monoclinic space group P21/n, with a Mo–C bond length of 2.40 A and a C–I bond length of 2.13 A. The compounds [Cp(CO)3W{(CH2)nX}] (X=Br, I; n=3–6) were also prepared in high yield and the crystal structures of [Cp(CO)3W{(CH2)5I}] and [Cp(CO)3W{(CH2)3Br}] are reported. The former compound forms orthorhombic crystals in the space group P21nb and the latter forms triclinic crystals in the space group P 1 . Both have W–C bond lengths of 2.35 A. The C–I bond length is 2.12 A; the C–Br bond length is 1.94 A.

The Os/Cu–Al-hydrotalcite catalysed hydroxylation of alkenes

A new Os/Cu-Al-hydrotalcite-like catalyst is described which, with N-methylmorpholine oxide as co-oxidant, heterogeneously catalyses the hydroxylation of olefins to give diols selectively and in high yield.

Bromo­propyl­di­carbonyl­(η5‐penta­methyl­cyclo­penta­dienyl)­iron(II)

In Cp*Fe(CO)2(n-C3H6Br), where Cp* = η5-C5(CH3)5, the Fe atom is coordinated by a pentaxadmethylxadcycloxadpentaxaddienyl ligand, two carbonyl ligands and a bromoxadalkyl chain in a pseudo-octahedral arrangement. The molecular geometry is similar to that reported for a related structure, with the alkyl chain in an all-trans conformation and a Fe—C(alkyl) bond length of 2.057u2005(3)u2005A. In the crystal structure, the molxadecules pack in layers.

[Di­carbonyl(η5-cyclo­penta­dienyl)­iron(II)]-μ2-1,3-propanediyl-[di­carbonyl(η5-cyclo­penta­dienyl)­ruthenium(II)]

The coordination of Fe and Ru in the title compound, [RuFe(C3H6)(C5H5)2(CO)4], is identical in its effectively tetrahedral form with that observed in closely analogous materials. However, partial [24.08u2005(17)%] disorder by interchange of Fe and Ru renders the bonds to Fe and Ru here apparently slightly longer and shorter, respectively, than they are in the analogues.

Quinoline-2-carbaldehyde

The title compound, C10H7NO, crystallizes with two almost planar molecules (A and B) in the asymmetric unit (r.m.s. deviations = 0.018 and 0.020u2005Å). In the crystal, the A molecules are linked by weak C—H⋯O interactions, thereby generating C(9) [001] chains. The B molecules do not exhibit any directional bonding interactions.

Tricarbonyl­(η5‐cyclo­pentadienyl)(3‐iodo­propyl)tungsten(II)

In the title compound, [W(C5H5)(C3H6I)(CO)3], the W atom is coordinated by a cycloxadpentadienyl ligand, three carbonyl ligands and an iodoxadalkyl chain in a distorted square-pyramidal arrangement. In the crystal structure, the molecules pack with the iodoxadalkyl chains in non-interdigitated layers.

Dichlorido{N-[2-(diphenylphosphanyl)benzylidene]-2-methylaniline}palladium(II) acetonitrile monosolvate

The title imino-phosphine compound, [PdCl2(C26H22NP)]·CH3CN, was prepared by reaction of N-[2-(diphenylphosphanyl)benzylidene]-2-methylaniline with dichlorido(cycloocta-1,5-diene)palladium(II) in dry CH2Cl2. The Pd(II) cation is coordinated by the P and N atoms of the bidentate chelating ligand and by two chloride anions, generating a distorted square-planar coordination geometry. There is a detectable trans influence for the chloride ligands. The methyl group present in this structure has an influence on the crystal packing.

Luminescence Properties of Eu- and Mg-Codoped Sol-Gel SiO2 Glasses

A series of SiO2 nanostructures codoped with Eu3+; Mg2+ ions were obtained by a sol-gel method. The gels synthesized by the hydrolysis of Si(OC2H5)4, Eu(NO3)3·6H2O, and Mg(NO3)2 were heated in air at 600°C for 2 hours. Firstly, the total amount of Eu3+ ions was varied from 0 to 2.0u2009mol% to investigate the effect of self-damping, while in the second case, the Eu3+ ions were kept constant in the experiment at 0.5u2009mol% total doping and Mg2+ ions varied. The samples were characterized by X-ray diffraction, TEM, EDS, and UV lamp-excited luminescence spectroscopy. The Eu3+ ions were homogeneously dispersed in the silica and interacting with the small (1–5u2009nm) amorphous silica matrix. Strong red emissions located at 614u2009nm and 590u2009nm for doped and codoped SiO2 were observed from the UV light excitation at room temperature. The composition of around 1.25u2009mol% Eu3+ gave highest emission intensity. SiO2; Mg2+ ions portray strongly enhanced emissions due to energy transfer from Mg2+ to Eu3+, which is due to radiative recombination. An increase in luminescence intensity was observed as the Mg2+-to-Eu3+ ratio increased for the range investigated. The results show Eu3+ ion is located inside or at the surface of disordered SiO2 nanoparticles.